U.S. patent number 10,975,267 [Application Number 15/509,359] was granted by the patent office on 2021-04-13 for anisotropic conductive film and connection structure.
This patent grant is currently assigned to DEXERIALS CORPORATION. The grantee listed for this patent is DEXERIALS CORPORATION. Invention is credited to Seiichiro Shinohara.
![](/patent/grant/10975267/US10975267-20210413-D00000.png)
![](/patent/grant/10975267/US10975267-20210413-D00001.png)
![](/patent/grant/10975267/US10975267-20210413-D00002.png)
![](/patent/grant/10975267/US10975267-20210413-D00003.png)
![](/patent/grant/10975267/US10975267-20210413-D00004.png)
![](/patent/grant/10975267/US10975267-20210413-D00005.png)
United States Patent |
10,975,267 |
Shinohara |
April 13, 2021 |
Anisotropic conductive film and connection structure
Abstract
An anisotropic conductive film including an electrically
insulating adhesive layer, and electrically conductive particles
disposed on the electrically insulating adhesive layer. In such an
anisotropic conductive film, the electrically conductive particles
are disposed in a lattice by being arranged in first direction rows
and second direction rows, and narrow and wide intervals are
provided between neighboring rows in at least one of the direction
rows. As a result, opposing terminals are stably connected using
the anisotropic conductive film, inspection after the connecting is
more easily performed, and the number of electrically conductive
particles not involved in the connection are reduced and, thereby,
the manufacturing cost of the anisotropic conductive film is
reduced, even in FOG connections or the like with finer bump
pitches.
Inventors: |
Shinohara; Seiichiro (Kanuma,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
DEXERIALS CORPORATION |
Tokyo |
N/A |
JP |
|
|
Assignee: |
DEXERIALS CORPORATION (Tokyo,
JP)
|
Family
ID: |
1000005484160 |
Appl.
No.: |
15/509,359 |
Filed: |
October 2, 2015 |
PCT
Filed: |
October 02, 2015 |
PCT No.: |
PCT/JP2015/078012 |
371(c)(1),(2),(4) Date: |
March 07, 2017 |
PCT
Pub. No.: |
WO2016/067828 |
PCT
Pub. Date: |
May 06, 2016 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20170278820 A1 |
Sep 28, 2017 |
|
Foreign Application Priority Data
|
|
|
|
|
Oct 28, 2014 [JP] |
|
|
JP2014-219785 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09J
9/02 (20130101); H01L 24/29 (20130101); H01R
11/01 (20130101); C08K 3/08 (20130101); H01L
24/83 (20130101); C09J 11/04 (20130101); H01B
1/22 (20130101); H01R 13/2414 (20130101); C09J
7/10 (20180101); C08K 2201/001 (20130101); C09J
2203/326 (20130101) |
Current International
Class: |
H01R
13/24 (20060101); C09J 9/02 (20060101); H01B
1/22 (20060101); H01L 23/00 (20060101); C09J
7/10 (20180101); H01R 11/01 (20060101); C09J
11/04 (20060101); C08K 3/08 (20060101) |
Field of
Search: |
;156/60 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2003-286457 |
|
Oct 2003 |
|
JP |
|
2007-080522 |
|
Mar 2007 |
|
JP |
|
4887700 |
|
Feb 2012 |
|
JP |
|
2014-063729 |
|
Apr 2014 |
|
JP |
|
WO-9745893 |
|
Dec 1997 |
|
WO |
|
Other References
Jul. 4, 2018 Office Action issued in Chinese Patent Application No.
201580055622.7. cited by applicant .
Dec. 15, 2015 International Search Report issued in International
Patent Application No. PCT/JP2015/078012. cited by applicant .
Dec. 15, 2015 Written Opinion of the International Searching
Authority issued in International Patent Application No.
PCT/JP2015/078012. cited by applicant .
Jan. 16, 2018 Office Action issued in Japanese Patent Application
No. 2014-219785. cited by applicant.
|
Primary Examiner: Orlando; Michael N
Assistant Examiner: Roldan; Christian
Attorney, Agent or Firm: Oliff PLC
Claims
The invention claimed is:
1. An anisotropic conductive film comprising: an electrically
insulating adhesive layer; and electrically conductive particles
disposed in the electrically insulating adhesive layer; wherein:
the electrically conductive particles are disposed in a lattice by
being arranged in first direction rows and second direction rows;
for at least one of the first and second direction rows, sparse
regions and dense regions of electrically conductive particles are
being formed by providing wide and narrow intervals between
neighboring rows; and the wide and narrow intervals are repeatedly
provided between the neighboring rows for the at least one of the
first and second direction rows.
2. The anisotropic conductive film according to claim 1, wherein:
at least one of the first and second direction rows include an
inter-row unit where a<b<c, where a, b, and c are three
distances between neighboring rows.
3. The anisotropic conductive film according to claim 1, wherein:
the at least one of the first and second direction rows provided
with the narrow and wide intervals therebetween are parallel with a
longitudinal direction of the anisotropic conductive film.
4. The anisotropic conductive film according to claim 2, wherein:
distances between the at least one of the first and second
direction rows in the inter-row unit geometrically change.
5. The anisotropic conductive film according to claim 2, wherein:
the distance b is not less than 0.5 times a particle size of the
electrically conductive particles.
6. A connection method for anisotropically conductively connecting
a terminal of a first electronic component and a terminal of a
second electronic component using the anisotropic conductive film
according to claim 1, the method comprising: among sparse regions
and dense regions of electrically conductive particles formed by
providing wide and narrow intervals between rows of electrically
conductive particles in the anisotropic conductive film, disposing
the dense regions between opposing terminals.
7. The connection method according to claim 6, wherein: rows
provided with narrow and wide intervals therebetween are disposed
so as to cross a longitudinal direction of the terminal.
8. A connection structure comprising: a first electronic component;
and a second electronic component, wherein the first electronic
component and the second electronic component are anisotropically
conductively connected using the anisotropic conductive film
according to claim 1.
9. A method of manufacturing a connection structure, comprising:
anisotropically conductively connecting a first electronic
component and a second electronic component using the anisotropic
conductive film according to claim 1.
10. The anisotropic conductive film according to claim 2, wherein
the distance a is more than zero.
11. The anisotropic conductive film according to claim 1, wherein
in either of the first and second direction rows, distances between
neighboring electrically conductive particles change regularly.
12. The anisotropic conductive film according to claim 1, wherein
in both of the first and second direction rows, distances between
neighboring electrically conductive particles change regularly.
13. The anisotropic conductive film according to claim 1, wherein
the electrically conductive particles are metal particles or
metal-coated resin particles.
14. The anisotropic conductive film according to claim 1, wherein
the electrically insulating adhesive layer is formed from a
plurality of resin layers.
15. The anisotropic conductive film according to claim 1, wherein
the first direction rows are orthogonal to the second direction
rows.
16. The anisotropic conductive film according to claim 1, wherein
electrically conductive particles disposed at both ends of the
first and second direction rows and corresponding electrically
conductive particles in at least two of the neighboring rows are
located in a same plane orthogonal to the anisotropic conductive
film.
17. The anisotropic conductive film according to claim 1, wherein
the dense regions of electrically conductive particles are
configured to be disposed only between a terminal of a first
electronic component and a terminal of a second electronic
component.
Description
TECHNICAL FIELD
The present invention relates to an anisotropic conductive film, a
connection method using the anisotropic conductive film, and a
connection structure connected via the anisotropic conductive
film.
BACKGROUND ART
Anisotropic conductive films are widely used when electronic
components such as IC chips are mounted on substrates. In recent
years, demand has arisen for high density wiring/interconnections
in small electronic devices such as mobile phones, and notebook
computers. A technique is known for utilizing an anisotropic
conductive film in such high density wiring/interconnections, in
which electrically conductive particles are evenly disposed in a
matrix in an electrically insulating adhesive layer of the
anisotropic conductive film.
However, there is a problem in that variations in connection
resistance occur even though the electrically conductive particles
are evenly disposed. This is because there are cases where the
electrically conductive particles located on the edges of terminals
are not sandwiched by vertically opposing terminals. To solve this
problem, a technique has been proposed in which a first row
direction of electrically conductive particles is configured as the
longitudinal direction of an anisotropic conductive film, and a
second row direction crossing the first row direction is configured
to be inclined at not less than 5.degree. and not greater than
15.degree. with respect to a direction orthogonal to the
longitudinal direction of the anisotropic conductive film (Patent
Literature 1).
CITATION LIST
Patent Literature
Patent Literature 1: Japanese Patent No. 4887700B
SUMMARY OF INVENTION
Technical Problem
However, for example, in cases of FPC on Glass (FOG) connections in
which a liquid crystal panel is connected to an FPC, it has been
difficult to obtain reliable conduction with the conventional
anisotropic conductive films described above when the size of the
connecting bumps becomes smaller and the pitch of the bumps becomes
finer. To solve this problem, simply increasing the disposition
density of the electrically conductive particles in the anisotropic
conductive film has been considered. However, there is still a
possibility that the electrically conductive particles will not be
sufficiently captured between opposing terminals that are
anisotropically conductively connected even if the disposition
density of the electrically conductive particles is increased.
Moreover, there is a problem in that the possibility of
short-circuiting increases due to the increased disposition density
of the electrically conductive particles. Additionally, there are
problems in that the number of electrically conductive particles
not involved with the connection increases unnecessarily, which
leads to increases in the manufacturing cost of the anisotropic
conductive film.
As such, an object of the present invention is to enable opposing
terminals to be stably connected using an anisotropic conductive
film, enable easier inspection after the connecting, and reduce the
number of electrically conductive particles not involved in the
connection, thereby reducing the manufacturing cost of the
anisotropic conductive film, even in FOG connections or the like
with finer bump pitches.
Solution to Problem
The present inventor discovered the following which resulted in the
completion of the present invention:
(1) In some cases, conduction cannot be obtained and/or
short-circuiting occurs when using, in a FOG connection, an
anisotropic conductive film in which electrically conductive
particles are evenly disposed and the disposition density of the
electrically conductive particles is simply increased. A reason for
the lack of conduction is because the electrically insulating resin
melted at a time of anisotropic conductive connecting flows in the
longitudinal direction of the terminals. This results in the
electrically conductive particles originally located on the
terminal flowing off the terminal and makes it impossible for the
terminal to capture the electrically conductive particles.
Additionally, a reason for the short-circuiting is because the
electrically conductive particles flow between terminals that are
neighboring in the horizontal direction, which results in the
electrically conductive particles becoming connected to each other
and causing the neighboring terminals to short circuit;
(2) When the electrically conductive particles are disposed in a
lattice in the electrically insulating adhesive layer, such
situations can be effectively prevented by providing narrow and
wide intervals between neighboring rows to form regions of dense
electrically conductive particles and regions of sparse
electrically conductive particles in the anisotropic conductive
film. When opposing terminals are anisotropically conductively
connected, the regions of dense electrically conductive particles
are disposed between opposing terminals and the regions of sparse
electrically conductive particles are disposed outside of the
opposing terminals;
(3) By forming these regions of sparse electrically conductive
particles, the number of electrically conductive particles not
involved in the connection can be reduced and, thus, the
manufacturing cost of the anisotropic conductive film can be
reduced; and
(4) When regions of sparse electrically conductive particles and
regions of dense electrically conductive particles are formed in
the anisotropic conductive film, products can more easily be
inspected after connecting by observing the density distribution of
the electrically conductive particles.
Specifically, the present invention provides an anisotropic
conductive film including an electrically insulating adhesive layer
and electrically conductive particles disposed in the electrically
insulating adhesive layer. In such an anisotropic conductive film,
the electrically conductive particles are disposed in a lattice by
being arranged in first direction rows and second direction rows;
and narrow and wide intervals are provided between neighboring rows
in at least one direction rows.
Additionally, the present invention provides a connection method
for anisotropically conductively connecting a terminal of a first
electronic component and a terminal of a second electronic
component using the anisotropic conductive film described above.
This connection method includes, among sparse disposition regions
and dense disposition regions of electrically conductive particles
formed by providing narrow and wide intervals between arrangements
of the electrically conductive particles in the anisotropic
conductive film, disposing the dense regions between opposing
terminals.
Furthermore, the present invention provides a connection structure,
including a first electronic component and a second electronic
component, wherein the first electronic component and the second
electronic component are anisotropically conductively connected via
the connection method described above.
Advantageous Effects of Invention
According to the anisotropic conductive film of the present
invention, the electrically conductive particles are disposed in a
lattice and narrow and wide intervals are provided between the rows
of the electrically conductive particles that form the lattice
disposition. As a result, regions of sparse electrically conductive
particles and regions of dense electrically conductive particles
are formed. Accordingly, when opposing terminals are
anisotropically conductively connected using the anisotropic
conductive film, the regions of dense electrically conductive
particles are disposed between the opposing terminals and the
regions of sparse electrically conductive particles are disposed in
regions outside the opposing terminals. As a result, electrically
conductive particles sufficient for ensuring conduction can be
captured on the terminals and short-circuiting between neighboring
terminals can be prevented, even if the electrically conductive
particles flow in the longitudinal direction of the terminals due
to the electrically insulating resin being melted at the time of
anisotropic conductive connecting.
Additionally, due to the regions of spare electrically conductive
particles and the regions of dense electrically conductive
particles being formed in the anisotropic conductive film, it is
easier to inspect products after connecting by observing the
density distribution of the electrically conductive particles.
Image analysis software or the like is used for such inspections,
and the inspections can be easily performed by measuring deviations
of the electrically conductive particles from preset locations.
Note that inspections using image analysis software may be
performed at a time of manufacturing the anisotropic conductive
film or before and after performing anisotropic conductive
connecting.
Furthermore, according to the anisotropic conductive film of the
present invention, the number of electrically conductive particles
not involved in the connection can be reduced and, thus, the
manufacturing cost of the anisotropic conductive film can be
reduced.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a disposition diagram of electrically conductive
particles in an anisotropic conductive film 1A of the Examples.
FIG. 2 is a cross-sectional view at a time of anisotropic
conductive connecting using the anisotropic conductive film 1A of
the Examples.
FIG. 3 is a disposition diagram of electrically conductive
particles in an anisotropic conductive film 1B of the Examples.
FIG. 4 is a disposition diagram of electrically conductive
particles in an anisotropic conductive film 1C of the Examples.
FIG. 5 is a disposition diagram of electrically conductive
particles in an anisotropic conductive film of Comparative Example
2.
DESCRIPTION OF EMBODIMENTS
Next, the present invention will be described in detail while
referring to the drawings. Note that in the drawings, identical
reference signs indicate the same constituents.
FIG. 1 is a disposition diagram of electrically conductive
particles 2 in an anisotropic conductive film 1A of an embodiment
of the present invention. In this anisotropic conductive film 1A,
the electrically conductive particles 2 are arranged in first
direction rows and second direction rows, thereby being disposed in
a lattice in an electrically insulating adhesive layer 3. More
specifically, the electrically conductive particles 2 are disposed
in first direction rows S (S1, S2, S3, S4 . . . ) parallel with a
longitudinal direction L1 of the anisotropic conductive film 1A,
and second direction rows T (T1, T2, T3, T4 . . . ) parallel with a
short-side direction L2 of the anisotropic conductive film 1A.
Among these, the first direction rows S are provided with narrow
and wide intervals between neighboring rows, and these narrow and
wide intervals repeat. That is, an inter-row unit U is repeated
such that a<b<c, where a, b, and c are three distances
between neighboring rows. Here, a.gtoreq.0 and when a=0, the
neighboring electrically conductive particles are in contact with
each other.
On the other hand, the second direction rows T are formed at equal
intervals.
As a result of the first direction rows and the second direction
rows, the anisotropic conductive film 1A is provided with regions
of sparse disposition density and regions of dense disposition
density of the electrically conductive particles 2.
In cases where a terminal of a first electronic component and a
terminal of a second electronic component are anisotropically
conductively connected using the anisotropic conductive film 1A, it
is preferable that a longitudinal direction of terminals 4
indicated by the dash lines in FIG. 1 be configured to be parallel
to the second direction rows T, and the first direction rows S be
oriented so as to cross the longitudinal direction of the terminals
4. As illustrated in FIG. 2, at a time of anisotropic conductive
connecting, terminals 4a and 4b and the anisotropic conductive film
1A are arranged such that the region of the anisotropic conductive
film 1A where the electrically conductive particles 2 are dense is
sandwiched between the terminal 4a of the first electronic
component and the terminal 4b of the second electronic component;
and are heat pressed using a heater 5 provided with a pressing
surface of a size that covers the rows of the terminals 4a and 4b.
During the heat pressing, the resin forming the electrically
insulating adhesive layer 3 melts. Due to the terminals 4a and 4b
existing on the edge side of the pressing surface of the heater 5,
when the melted resin flows in the longitudinal direction (arrow A)
of a terminal 4, the electrically conductive particles 2 on the
terminals 4a and 4b and also the electrically conductive particles
2 between the terminals neighboring in the horizontal direction
(between neighboring terminals 4a or between neighboring terminals
4b) move in the direction of the arrow A. However, because the
region of the anisotropic conductive film 1A where the electrically
conductive particles 2 are dense is sandwiched between the
terminals 4a and 4b, even if there are electrically conductive
particles 2 that flow away from the terminals 4a and 4b due to the
flow of the resin, electrically conductive particles 2 sufficient
to ensure the conduction of the terminals 4a and 4b can be
captured. Therefore, the terminals 4a and 4b are connected by the
electrically conductive particles 2, as depicted by the dash lines.
Additionally, the region where the electrically conductive
particles 2 are sparse exists in the direction of the arrow A on
the outside of the region formed between the neighboring terminals
and juxtaposed with the terminals. Therefore, compared to cases in
which only regions of dense electrically conductive particles 2 are
formed, the electrically conductive particles 2 can be prevented
from connecting to each other due to the movement of the
electrically conductive particles 2 in the direction A and,
particularly, connecting of three or more of the electrically
conductive particles 2 can be prevented. As a result,
short-circuiting between terminals neighboring in the horizontal
direction due to connected electrically conductive particles 2 can
be prevented.
Here, to reliably capture the electrically conductive particles 2
on each of the terminals 4 at the time of anisotropic conductive
connecting, it is preferable that the sum of the three distances a,
b, and c between the neighboring rows be less than the length in
the longitudinal direction of the terminal 4. This is because, from
the perspective of the stability of the anisotropic connection, at
least three of the electrically conductive particles preferably
exist on the terminal.
Additionally, there is a concern in that if the sparse/dense
balance of the electrically conductive particles 2 is lost, uneven
contact could occur due to the same trend occurring throughout the
entirety of the terminal rows that are formed at a predetermined
pitch, and reliability and the like would be negatively affected.
On this point, to ensure the uniformity of the electrically
conductive particles at the time of pressing, the distance b is
preferably not less than 0.5 times, more preferably from 0.5 to 150
times, and even more preferably from 0.75 to 100 times a particle
size of the electrically conductive particles 2. The distance c is
preferably 0.5.times. an integral multiple with respect to the
distance b. This is because with such a configuration, it will be
easy to compare the distance c with the distance b.
Furthermore, to facilitate pass/fail judgment before and after the
connecting, the distances a, b, and c preferably are provided with
a geometric relationship. In an example of such a configuration,
b/a=c/b=1.2 to 5. Alternatively, if the distance is configured as
an integral multiple 1/2 the particle size, one particle can be
used as the criteria (measure). As a result, the uniformity of the
pressing is easily recognized even after the anisotropic conductive
connecting and, therefore, connection problems in connection
structures are easily determined.
On the other hand, from the perspective of preventing
short-circuiting and improving conduction reliability, the
intervals between the second direction rows T1, T2, T3, T4 . . .
that are parallel to the short-side direction of the anisotropic
conductive film 1A preferably are configured to be not less than
0.5 times the average size of the electrically conductive
particles. This distance is appropriately calculated on the basis
of the bump layout of the anisotropic connection. This is because
it is not possible to perfectly predict the direction that the
resin melted at the time of anisotropic conductive connecting will
flow, and flow of the resin may be random on the terminals or
thereabout.
In the anisotropic conductive film 1A, from the perspective of
preventing short-circuiting and the stability of the connection of
the opposing terminals, a particle size D of the electrically
conductive particles 2 is preferably from 1 to 10 .mu.m.
A density of the electrically conductive particles 2 is preferably
from 2000 to 250000 particles/mm.sup.2. This particle density is
appropriately adjusted depending on the particle size and the
direction in which the electrically conductive particles 2 are
disposed.
In the anisotropic conductive film 1A, the constituent material of
the electrically conductive particles 2 themselves and the layer
structure or constituent resin of the electrically insulating
adhesive layer 3 can take various forms.
That is, any material used in conventional anisotropic conductive
films may be appropriately selected and used as the electrically
conductive particles 2. Examples thereof include nickel, cobalt,
silver, copper, gold, palladium, and similar metal particles,
metal-coated resin particles, and the like. A combination of two or
more materials may also be used.
Any electrically insulating resin layer used in conventional
anisotropic conductive films may be appropriately used as the
electrically insulating adhesive layer 3. Examples thereof include
a photo-radical polymerization type resin layer containing an
acrylate compound and a photo-radical polymerization initiator, a
thermal radical polymerization type resin layer containing an
acrylate compound and a thermal radical polymerization initiator, a
thermal cationic polymerization type resin layer containing an
epoxy compound and a thermal cationic polymerization initiator, a
thermal anionic polymerization type resin layer containing an epoxy
compound and a thermal anionic polymerization initiator, and the
like. Additionally, as necessary, polymerized products of these
resin layers may be used. Moreover, the electrically insulating
adhesive layer 3 may be formed from a plurality of resin
layers.
The anisotropic conductive film of the present invention can take
various forms. For example, as with an anisotropic conductive film
1B illustrated in FIG. 3, in contrast with the anisotropic
conductive film 1A described above, a configuration is possible in
which the first direction rows S parallel with the longitudinal
direction L1 of the anisotropic conductive film are configured at
even intervals, and the second direction rows T parallel with the
short-side direction of the anisotropic conductive film 1B are
provided with narrow and wide intervals. That is, the unit U is
repeatedly provided in the second direction rows T such that
a<b<c, where a, b, and c are three distances between
neighboring rows in the second direction rows T.
In this case, as with the distances a, b, and c between the rows S
in the anisotropic conductive film 1A, the distance b between the
rows T is preferably not less than 0.5 times, more preferably from
0.5 to 150 times, and even more preferably from 0.75 to 100 times a
particle size of the electrically conductive particles 2.
Additionally, the sum of the distances a, b, and c is preferably
configured to be less than 0.4 mm.
In the anisotropic conductive film 1B, the interval between the
first direction rows S is preferably configured to be not less than
0.5 times and is more preferably configured to be an integral
multiple of 1/2 the particle size of the electrically conductive
particles 2. This allows the rows of electrically conductive
particles to be used as one criteria (measure) for determining the
state after the anisotropic conductive connecting.
A length of the bumps sometimes exceeds the short-side direction
(width) of the film and, as such, there is no need to impose an
upper limit on the number of electrically conductive particles that
exist in the longitudinal direction of the bumps. However, there
are preferably three or more and more preferably four or more of
the electrically conductive particles in the short-side direction
(width) of the anisotropic conductive film at the time of
connecting.
As described above, the anisotropic conductive film 1B is provided
with narrow and wide intervals between the second direction rows T.
As such, in cases where the resin melted at the time of anisotropic
conductive connecting flows in the short-side direction of the
terminals 4, the capturing performance of the electrically
conductive particles 2 on the terminals 4 can be ensured and
short-circuiting can be prevented.
Additionally, as with an anisotropic conductive film 1C illustrated
in FIG. 4, in contrast with the anisotropic conductive film 1A
described above, a configuration is possible in which the first
direction rows S parallel with the longitudinal direction L1 of the
anisotropic conductive film are provided with narrow and wide
intervals and, also, the second direction rows T parallel with the
short-side direction of the anisotropic conductive film 1C are
provided with narrow and wide intervals.
In this case, narrow and wide intervals are provided between both
the first direction rows S and the second direction rows T. As
such, even in cases where the resin melted on the terminal 4 or
thereabout at the time of anisotropic conductive connecting flows
randomly, the capturing performance of the electrically conductive
particles 2 on the terminal 4 can be ensured and short-circuiting
can be prevented.
Furthermore, in the anisotropic conductive films 1A, 1B, and 1C
described above, in the case where two narrow and wide distances a
and b between neighboring rows are provided and these narrow and
wide distances are repeated between the rows, the repeating unit
may be constituted by only the two distances a and b between the
rows.
From the perspective of easily recognizing the rows of the
electrically conductive particles in the anisotropic conductive
film (reducing the number of steps in the inspection process), the
repeating unit preferably spans across three or more intervals
between the rows, and distances a<b<c are preferably
satisfied. This is because long/short is easily identified when
there are three distance settings between the rows compared to two.
This configuration is particularly effective when the difference
between distances a and b is comparatively small.
Furthermore, the distance c between the rows may be configured to
be double a distance between the rows in a case where the narrow
and wide distances between the rows are not provided, and one of
the rows in the lattice arrangement of the electrically conductive
particles may be repeatedly eliminated.
Additionally, the first direction rows S and the second direction
rows T need not be orthogonal to each other. One or both of the
rows may be inclined with respect to the longitudinal direction of
the anisotropic conductive film. Typically, rows of terminals to be
anisotropically connected are constituted by terminals 4 having the
same rectangular shape being arranged at a predetermined interval
in a single direction. As such, one or both of the first direction
rows S and the second direction rows T are configured as rows
inclined with respect to the longitudinal direction of the
anisotropic conductive film and stacked on the row of terminals to
be anisotropically connected. This allows detection to be
comparatively easier in cases where there is an abnormality in the
lattice arrangement of the electrically conductive particles.
An example of a method for fixing the electrically conductive
particles 2 in the electrically insulating adhesive layer 3 at the
arrangement described above includes fabricating a mold having
recesses corresponding to the arrangement of the electrically
conductive particles 2 by machining, laser processing,
photolithography, or the like; placing the electrically conductive
particles into the mold; filling the mold with an electrically
insulating adhesive layer forming composition; curing; and removing
the product from the mold. A mold made from a material with lower
rigidity may be fabricated from this mold.
Additionally, a method including providing a member, which includes
through-holes defined in a predetermined arrangement, on the
electrically insulating adhesive layer forming composition;
supplying the electrically conductive particles 2 from there above;
and causing the electrically conductive particles 2 to pass through
the through-holes may be used to place the electrically conductive
particles 2 in the electrically insulating adhesive layer 3 at the
arrangement described above.
Additionally, in cases where the terminal of an IC chip, an IC
module, a liquid crystal panel or similar first electronic
component and the terminal of a flexible board or similar second
electronic component are anisotropically conductively connected by
use of the anisotropic conductive film of the present invention,
and in cases where the terminal of an IC chip, an IC module, or
similar first electronic component and the terminal of a glass
board or similar second electronic component are anisotropically
conductively connected by use of the anisotropic conductive film of
the present invention, as illustrated in FIG. 1, of regions of
sparse electrically conductive particle 2 and regions of dense
electrically conductive particle 2 formed by providing the narrow
and wide intervals between the rows of the electrically conductive
particles 2 in the anisotropic conductive film, the regions of
dense electrically conductive particles 2 are disposed between the
opposing terminals 4. The present invention also includes
connection structures connected in this manner.
Particularly, from the perspective of preventing short-circuiting
between the terminals in the connection structure, the rows
provided with the narrow and wide intervals between the rows of
electrically conductive particles is preferably arranged so as to
cross the longitudinal direction of the terminals.
EXAMPLES
Next, the present invention will be described in detail on the
basis of examples.
Examples 1 to 10, Comparative Examples 1 and 2
To investigate the relationship between the arrangement of the
electrically conductive particles in the anisotropic conductive
film and conduction characteristics, the anisotropic conductive
films shown in Table 1 were manufactured. Here, AUL704
(manufactured by Sekisui Chemical Co., Ltd.; Particle size: 4
.mu.m) was used as the electrically conductive particles, and the
electrically insulating adhesive layer was formed as follows from a
mixed solution containing 60 parts by mass of YP-50 (manufactured
by Nippon Steel & Sumikin Chemical Co., Ltd.; thermoplastic
resin), 60 parts by mass of jER828 (manufactured by Mitsubishi
Chemical Corporation; thermosetting resin), and 2 parts by mass of
SI-60L (manufactured by Sanshin Chemical Industry Co., Ltd.; latent
curing agent). Specifically, this mixture was coated on a PET film
having a film thickness of 50 .mu.m, and dried in an oven at
80.degree. C. for 5 minutes. Thus, an adhesive layer having a
thickness of 20 -82 m was formed on the PET film.
On the other hand, molds having convex row patterns at the
arrangements illustrated in Table 1 were fabricated, conventionally
known transparent resin pellets were melted and, while melted,
poured into the molds, and the melted transparent resin was cooled
and allowed to harden. Thus, resin molds having convexities in the
row patterns illustrated in Table 1 were formed. The convexities of
the resin molds were filled with the electrically conductive
particles, and the adhesive layer, namely the electrically
insulating adhesive layer described above, was placed thereon.
Then, the curable resin included in the electrically insulating
adhesive layer was cured by UV curing. Then, the electrically
insulating adhesive layer was peeled from the mold. Thus, the
anisotropic conductive films of the Examples and Comparative
Examples were manufactured.
Note that in Comparative Example 1, the electrically conductive
particles were disposed randomly on the same plane by disposing the
electrically conductive particles in a low-boiling point solvent
and then spraying the mixture at the target.
Evaluation
The (a) initial conduction resistance, (b) conduction reliability,
and (c) number of connected particle clusters of the anisotropic
conductive films of the Examples and the Comparative Examples were
each evaluated as follows. Results are shown in Table 1.
(a) Initial Conduction Resistance
The anisotropic conductive film of each of the Examples and the
Comparative Examples was sandwiched between a flexible printed
circuit (FPC) and a glass board and heat pressed (180.degree. C.,
80 MPa, 5 seconds) so as to obtain each connected object for
evaluation. Conduction resistance of each connected object for
evaluation was measured.
Here, the terminal patterns of the FPC and the glass board
corresponded to each other, and sizes thereof were as described
below.
Additionally, the longitudinal direction of the anisotropic
conductive film and the short-side direction of the bumps were
aligned and affixed to each other.
FPC
Bump pitch: 32 .mu.m
Bump width: 16 .mu.m; Space between bumps: 16 .mu.m
Bump length: 1 mm
Glass board
ITO Solid Glass
(b) Conduction Reliability
The conduction resistance after placing the connected objects for
evaluation, fabricated in (a) using the anisotropic conductive
films of the Examples and the Comparative Examples, in a
thermostatic chamber set to a temperature of 85.degree. C. and a
humidity of 85% RH for 500 hours was measured in the same manner as
(a). Note that from the perspective of practical conduction
stability of a connected electronic component, the conduction
resistance preferably does not exceed 5 .OMEGA..
(c) Number of Connected Particle Clusters
The connected objects for evaluation, fabricated in (a) using the
anisotropic conductive films of the Examples and the Comparative
Examples, were observed under a microscope, the number of connected
particle clusters where two or more of the electrically conductive
particles were connected was counted, and the number of connected
particle clusters per 100 electrically conductive particles was
calculated.
TABLE-US-00001 TABLE 1-1 Comparative Comparative Example Example
Example Example 1 Example 2 1 2 3 Electrically conductive 4 4 4 4 4
particle size (.mu.m) Number density of 17400 17400 17400 14400
12100 electrically conductive particles (particles/mm.sup.2) Row
pattern of Random Square lattice FIG. 3 electrically conductive
(FIG. 5) particles Distance a (.mu.m) -- 3.6 2 2 4 between b
(.mu.m) -- 3 4 6 rows c (.mu.m) -- 4.5 8 9 d (.mu.m) -- 4 4 4 (a)
Initial (.OMEGA.) 1.3 1.2 1.2 1.2 1.8 Conduction Resistance (b)
Conduction (.OMEGA.) 4 4 4 4.5 5 Reliability (c) Number of
Connected 25 20 14 6 2 Particle Clusters (per 100 particles)
TABLE-US-00002 TABLE 1-2 Example Example Example Example Example
Example Example 4 5 6 7 8 9 10 Electrically conductive 4 4 4 4 4 4
3 particle size (.mu.m) Number density of 17400 14400 12100 19500
13300 9400 12300 electrically conductive particles
(particles/mm.sup.2) Row pattern of FIG. 1 FIG. 4 FIG. 1
electrically conductive particles Distance a (.mu.m) 2 2 4 2 2 4 3
between b (.mu.m) 3 4 6 3 4 6 6 rows c (.mu.m) 4.5 8 9 4.5 8 9 9 d
(.mu.m) 4 4 4 (a) Initial (.OMEGA.) 1.3 1.8 2.2 1.3 1.2 1.3 2.1
Conduction Resistance (b) Conduction (.OMEGA.) 4 4.5 5 4 4 4 5
Reliability (c) Number of Connected 12 8 4 8 4 2 4 Particle
Clusters (per 100 particles)
From Table 1, it is clear that the number of connected particle
clusters in the connected objects for evaluation of Examples 1 to
10 was significantly less than the number of connected particle
clusters in the connected object for evaluation of Comparative
Example 1 and that short-circuiting does not occur as easily. The
number of connected particle clusters in the connected objects for
evaluation of Examples 1 to 10 was less than the number of
connected particle clusters in the connected object for evaluation
of Comparative Example 2. Moreover, while the locations where the
connected particles formed were random in Comparative Example 2,
regularity was found in the Examples. That is, it was confirmed
that the locations where short-circuiting occurs are controlled and
that short-circuiting risk itself was reduced.
Additionally, the number density of the electrically conductive
particles in each of the anisotropic conductive films of Examples
2, 3, 5, 6, 8, 9, and 10 was less than the anisotropic conductive
films of Comparative Examples 1 and 2. Regardless of this, it is
clear that the anisotropic conductive films of Examples 2, 3, 5, 6,
8, 9, and 10 displayed initial conduction and conduction
reliability of the same level as the connected objects for
evaluation of Comparative Examples 1 and 2, the number of
electrically conductive particles needed to ensure conduction could
be reduced, and the manufacturing cost of the anisotropic
conductive film could be reduced.
REFERENCE SIGNS LIST
1A, 1B, 1C Anisotropic conductive film 2 Electrically conductive
particle 3 Electrically insulating adhesive layer 4, 4a, 4b
Terminal 5 Heater a, b, c Distance between rows L1 Longitudinal
direction of anisotropic conductive film L2 Short-side direction of
anisotropic conductive film (longitudinal direction of connection
terminal) S, S1, S2, S3, S4 First direction row T, T1, T2, T3, T4
Second direction row U Inter-row unit D Particle size of
electrically conductive particles
* * * * *